Prevent installation of new APEX.

This was previously only done on user build and the code convergence
caused bugs that we haven't spotted for a while.

Change-Id: Ib7f51b5ef6d3f221483eb2e2dcb2f4d19a0fbbee
Fixes: 132429173
Test: APEX CTS tests on both user and userdebug builds
1 file changed